When La Forge and Wesley complain privately to Riker in Ten Forward about this, he reminds them that Kurn simply has a different style of command and that Klingons believe in obedience and strict adherence to regulations. However, it is notable that the only person Kurn has not been giving a hard time is "the one person who wouldn't really mind it": Worf.

Kurn gives Worf easy assignments and praises him sarcastically for his efficiency during a minor course correction on the bridge. Worf angers at being patronized.

While in a turbolift on his way to the captain's dining room, Riker tells Kurn it took him some getting used to Klingon culture while serving on the Pagh. He offers to assist Kurn with suggestions in working with the crew. Kurn respectfully declines the offer, reminding Riker that on a Klingon ship, he would be killed for such a "suggestion".

A special dinner is prepared at the captain's mess in honor of Kurn, who understands the honor and is prepared to sample some of the food, even though some of it is cooked -- but he doesn't like it, and bluntly explains that it is too bland. La Forge observes that it seems to agree with Worf, earning Worf a contemptuous look from Kurn.

After dinner, filled with rage, Worf goes to Kurn's quarters to demand an explanation. When the other expresses doubt of Worf's Klingon instincts, Worf erupts in a violent outburst. Kurn is pleased and says he's been testing Worf to see just how Klingon he was, revealing that he is really Worf's younger brother.

Kurn explains that when Mogh's family went to Khitomer, he had been left behind with their father's friend, Lorgh, and so escaped the massacre.
Worf explains to Kurn that the Starfleet officer that rescued him was told by the Klingon High Command that he had no living relatives, believing that Kurn was with the family and therefore killed at Khitomer. After the massacre, Lorgh adopted Kurn as his son and kept him in his family. When Kurn reached the age of ascension he was told the truth about his bloodline.

Kurn has sought Worf out because their father, Mogh, is accused of treason by the Klingon High Council. Supposedly, he had given the Romulans defense access codes allowing them to lower the shields of the Khitomer outpost just before the Romulan attack. Kurn had lived all these years, hiding his identity by masquerading as the son of Lorgh, but when he learned of the Council's action he came to Worf, asking him to challenge the judgment as Mogh's elder son.

Picard says that since Worf is accused of a capital crime it would be better if he were standing at Worf's side as he made his challenge, rather than simply granting him shore leave. Picard commands Kurn to set course for the First City of the Klingon homeworld. Kurn is surprised; he hadn't expected the Enterprise itself to change course. Now he respects Worf more deeply than ever.

On the way home, Kurn asks Worf if he can be his Cha'DIch, or ritual second; while Worf is accused, he will not be allowed in any duels or fights. Worf accepts, although he tells Kurn that he must not reveal his true bloodline, reminding Kurn that while on the Enterprise it's proper for Worf to obey Kurn; but in Council, Kurn will have to obey Worf, who is older.

Once they arrive at Qo'noS, Worf and Kurn beam down with Picard and Riker accompanying them. Worf pronounces his challenge before the Council and faces the accusations of Duras, the son of Mogh's greatest rival. Worf acknowledges that he is prepared to face the consequences with his very life if his challenge fails. "I am Worf, son of Mogh. I have come to challenge the lies that have been spoken of my father!", he defiantly states to the High Council.

Duras accuses Worf of forsaking his heritage for the Federation, but Picard tells the council that Worf has served under his command with distinction, earning Picard's admiration and respect. Appealing to the council's better natures, Picard says he trusts their wisdom will guide them to clear Worf's family name and return him to duty. Chancellor K'mpec notes the trust of a commanding officer is admirable and notes it for the record.

Duras testifies that a transmission of access codes went out from the outpost to the Romulan vessels which allowed them to dismantle the outposts' shields. Thousands of Klingons died on Khitomer, including Duras' father. Duras calls Mogh a traitor and because Worf has brought this challenge, Duras calls him a traitor as well, backhanding Worf in the traditions of their people. Duras then rips Worf's baldric off of him, telling Worf he is unworthy to wear the emblems of their people. Worf tells Duras "it is a good day to die, but the day is not yet over."

During a recess of the council, K'mpec meets with Worf and tries to persuade him into abandoning his challenge. Worf reacts with shock and dismay at this seemingly un-Klingon request, even though he understands that K'mpec's personal affection for Mogh may be influencing the request.

Kurn has received a note to meet someone in an isolated corridor; it is Duras. Duras reveals that he knows Kurn's true bloodline and tries to blackmail him into turning against Worf. Kurn refuses, and Duras' assassins attack and seriously wound him.

Although Beverly Crusher reassures Worf that Kurn's wounds are not life-threatening, Worf tells her she should have let him die because he'll be executed anyway. Worf asks Picard to be his Cha'DIch. Picard demurs, but Worf insists that there is no one better qualified. Picard accepts and recites the traditional Klingon words which mean "I accept with honor. May your enemies tremble before you."

Surprised by Worf's new Cha'DIch, Duras questions Picard's valditiy as Cha'DIch but Picard tells Duras that he's not here to command, to which Duras responds that he has to fight as well, which isn't something that is taught by Starfleet. Picard defiantly tells Duras that he is welcome to test that assumption at his leisure.

The Enterprise crew, on Picard's orders, are investigating the Khitomer massacre on their own. The USS Intrepid was the first ship on the scene of the disaster; Data contacts Starfleet for copies of the Intrepid's logs. Meanwhile, La Forge and Data have gotten into the Klingon central information net and discovered that the Klingons recently captured a Romulan ship with information about Khitomer in the ship's logs and that's how they found out about the treachery.

Upon comparing the information in the Klingon archives with the Intrepid logs, La Forge and Data discover that there is a discrepancy in the transmissions. The evidence which supported Mogh's guilt was faked. Another survivor of the Khitomer Massacre, a woman named Kahlest, is found. Picard is told about this by Riker during the second Council session and asks Worf, who says that Kahlest was his nurse and that he thought she had died. Picard tells Worf he must find her and bring her before the Council. Worf recommends that he not go alone, as it is too dangerous. Picard tells him, "Hey, I'm your Cha'DIch."

Using a cloak and keeping the hood up, Picard journeys into the Old City and finds Kahlest's home. Kahlest says she considers her life over after Khitomer and she is waiting to die. Picard tries to persuade Kahlest to accompany him back to the High Council chamber, telling her that the family that she once served proudly needs her again. She refuses, and Picard starts to leave. Just outside Kahlest's door, he is ambushed by Duras' assassins. He manages to overcome one, Kahlest emerges from her home, and throws a knife, killing the other. Kahlest now agrees to accompany Picard back to the High Council for the purpose of testifying for Worf. She also reveals that K'mpec was once romantically interested in her, but she wasn't attracted to him; he was too fat.

Just as K'mpec is about to pronounce judgment on Worf, Picard enters with Kahlest. In a private session, Picard demands that she be allowed to testify in open council in accordance with Klingon law. Duras is almost hysterically against it. K'mpec silences him by asking him if he would really kill an old woman to cover his dishonor. K'mpec's statement makes it clear that the dishonor rests not on Worf but on Duras; Kahlest is free to go. K'mpec tells Kahlest, "It is good to see you again", to which she responds, "You are still fat, K'mpec."

K'mpec privately explains the truth. When Klingons captured the Romulan ship with the records, they learned of the treachery behind the Khitomer Massacre; this soon became common knowledge, and someone had to answer for that treachery. Fortunately, only the Council knew who transmitted his code: not Mogh, but Ja'rod: Duras' father. K'mpec says the Duras family was too powerful and to expose him would likely split the Empire and cause a civil war. In order to avoid that, they decided to use Mogh as a scapegoat, believing that Worf, since he was in Starfleet, would not challenge the judgment. None of them realized that Kurn was Mogh's second child. Picard says this means Worf's challenge was successful. He refuses to hand Worf and Kurn over for execution. When K'mpec threatens to end the alliance with the Federation because of Picard's defiance, Picard reminds him that their alliance is not based on lies. If they must protect their secrets, then so be it but Picard will not allow the needless sacrifice of these two men.

Worf speaks up and says he'll volunteer to die for the sake of the Klingon Empire. Picard begins to object but Worf tells his Cha'DIch to be silent. Worf asks for Kurn's life to be spared. Duras rejects this, as Kurn's honor would then demand revenge. Worf then offers to accept discommendation if Kurn will be allowed to live. K'mpec tells Worf that doing so would be the same as admitting his father's guilt. Worf simply says "So be it." K'mpec states that Worf's heart is truly Klingon, and commands that this will never be spoken of again to anyone. Before they proceed, Worf calls Duras the son of a traitor and backhands him as tradition demands.

Kurn is heartbroken by Worf's decision, telling Picard that he was ready to die for Worf. Picard tells Kurn that he must live in order to restore the honor of Mogh's family. Picard tells Kurn that there will be another day. "Do not forget what he does here today. Do not let your children forget." Picard and Kurn join Worf in the middle of the council chambers and the council members gather in a circle around Worf. Worf says the ritual words, "tlhIH ghIj jIHyoj" ("I fear your judgment"); K'mpec replies, "biHnuch!" ("Coward!"), and one by one, the Council members cross their arms and turn their backs (turning to their right) on him in ritual ostracism. Worf softly tells Kurn that he must do it also. Almost on the verge of tears, Kurn very reluctantly complies, but instead of turning to his right, he turns to his left. The whole assembly having turned their backs, Worf and Picard leave the Council Chamber and return to the Enterprise.

"I imagine it must be very difficult for you to work with a crew that is so different. I would be happy to guide you in that regard, if it would be helpful."
"No Commander, it wouldn't."
"This is not a Klingon ship, sir."
"No Commander, it is not. If it were a Klingon ship, I would've killed you for offering your suggestion."

- Riker and Kurn

"How long has this bird been dead? It appears to have been lying in the sun for quite some time."
"Well it's not dead, it's been replicated. And you do understand that we cook most of our foods..."
"Ah yes, I was told to prepare for that. I shall try some of your burned replicated bird meat."

- Kurn and La Forge

"I never kill anyone at the supper table, Mr. La Forge."

- Kurn

"I am Klingon! If you doubt it, a demonstration can be arranged."
"That is a response of a Klingon. The response I would expect from my older brother."

- Worf and Kurn

"Will you grant my leave, Captain?"
"No - if I understand correctly, a Starfleet officer, a respected member of my crew, could be charged with a capital crime. Your actions on this matter will reflect on this ship, and on the Federation - therefore, it seems only appropriate that your captain should be at your side while you make your challenge... I'm sure you would do no less for me."

- Worf and Picard

"I am Worf, son of Mogh. I have come to challenge the lies that have been spoken of my father!"

- Worf, to the Klingon High Council

"I should've known. Worf was right. It is a good day to die."
"The time has not yet come. It does not have to come for many turns. I know who you are, Kurn, son of Mogh."
"What?!"
"It was a wise choice to hide your family name. Do not err now by embracing it again, for you only embrace death."
"We shall see."
"Worf has made a choice and he will die for it. But you can still be safe. Let him stand alone."
"He is my brother! I will not betray him!!"
"Then you will die for him!!"

- Kurn and Duras

"Are you adjusting to your new environment, Commander?""I find the constraints a bit difficult to conform to. Just a short while ago I had to stop myself from killing Commander Riker."

- Troi and Kurn

"For many turns, the truth about Khitomer has been dormant. Unknown. Now the truth has been revealed. The traitor, Mogh, sent the defense access codes to the Romulan patrol ships, allowing them to destroy the outpost. Thousands died on Khitomer! My father died on Khitomer! Their deaths must be avenged. Your father was a traitor. By posing this challenge, you are a traitor! You will not wear the emblems of our people. You are a fool, and your challenge can only result in a fool's death."
"It is a good day to die, Duras, but the day is not yet over."

- Duras and Worf

"This is not your world, human. You do not command here."
"I'm not here to command."
"Then you must be ready to fight. Something Starfleet does not teach you."
"You may test that assumption at your convenience."

- Duras and Picard

"My appreciation, madam."

- Picard, to Kahlest after she kills a Klingon who was about to murder him

"This Ha'DIbaH should've been fed to the dogs!"

- Worf, pointing at Duras

"You are brave, cha'DIch. Worf chose well."

- Kahlest, after Picard fights off Duras's assassins

"K'mpec would remember Kalest. I caught his eye back then. But he was too fat."

- Kahlest

"It is good to see you again."
"You are still fat, K'mpec."

- K'mpec and Kahlest

"You admit the truth, and yet you expect him to accept punishment? What does this say of an empire who holds honor so dear?"
"The empire will not be destroyed for one family's honor."
"Unacceptable, K'mpec!"
"You have no say in this, cha'DIch!"
"I speak now as the captain of the USS Enterprise and Lieutenant Worf's commanding officer! You will not execute a member of my crew, nor will I turn his brother over to you!"
"This is not the Federation, Picard. If you defy an order of the High Council, the alliance with the Federation could fall to dust."
"The alliance with the Federation is not based on lies, K'mpec. Protect your secrets if you must, but you will not sacrifice these men."

This story began life as two different scripts, one by Drew Deighan which featured Worf's father being accused of treason, and another script by Beth Woods, in which Worf's brother came aboard the Enterprise. Shortly after officially joining the writing staff, Ronald D. Moore was given the two scripts by Michael Piller and asked to combine them into a single story. (TNG Season 3 Blu-ray, episode commentary)

Moore recalled, "I was in love with 'Sins of the Father' and I fought for it when there was some question about which way we were going to go with it. I really like the fact Worf took it on the chin that episode. It said he was willing to stand up and do the right thing for his people, even if they weren't going to do the right thing by him. Patrick and I were at the Saturn Awards together, and he made a really good suggestion. When Worf is asking Picard to be his Cha'DIch, Picard originally says a single Klingon word, but Patrick thought it would be nice if Picard knew the whole line of ritual. At that time there wasn't a formal ritual, and there wasn't one for Kurn either, so I went back and wrote a line for him to say in Klingon and I tied it into Picard." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 193)

Director Les Landau recalled, "Here was an opportunity to explore the Klingon world in depth from beginning to end. Meaning that Ron Moore came up with a wonderful story which Richard James, the art director, and Jim Mees, the set decorator, had to visualize in terms of set design and set decoration. Additionally, to which Marvin Rush, the cameraman, had to conceptually find a visual representation of what the Klingon world was all about. I think all three of those gentlemen accomplished that task totally. In fact, Richard and Jim went on to win Emmy Awards for that episode, which I'm very proud of. Marvin's work speaks for itself. It was visually one of the most dynamic episodes ever done. It looks like a feature film. There were long detailed conversations about how, conceptually, we should deal with them. Ultimately, Rick Berman gave the final approval for each and every one of the ideas and details, and we showed a world that was heretofore never seen before, and which the audience craves to see more of. I was never one of the original Star Trek fans, however. My attitude was, is and always will be to never see what has come before, but to go where none have before and visualize what is in my thinking and mind as to what the visuals should be, which is dictated by the storyline. We must always come back to the words and what the story is, because without it, we have nothing to tell. After all, film and episodic television is nothing if not telling a story." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 194)

The design of the Klingon Great Hall (and other sets in the episode) won an Emmy Award for Best Art Direction for Star Trek: The Next Generation production designer Richard James. The exterior of the Great Hall and the surrounding First City was a matte painting created by Syd Dutton at Illusion Arts. (Star Trek Encyclopedia 1st ed., p. 118)

Kahlest tells Picard that Mogh "was loyal to the emperor." However, "Rightful Heir" will later establish that the Klingons haven't had an emperor in 300 years. Thus, we must assume that Kahlest was abstractly referring to the Emperor Kahless and his guiding principles for all Klingons.

This is the only episode where Duras' father, Ja'rod, is actually named.

Picard refers to the Klingon state as the "Klingon Imperial Empire," a redundant designation which was never used again.

Moore remarked, "I thought Tony Todd did a wonderful job as Worf's brother. I was kind of worried, because there's always that hesitation when you're bringing in other family members no one else has even seen. Half the audience is ready to throw things at the screen, and you're thinking, 'This better work.' I was there when he stepped on the stage and made it his own." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 193)

Moore saw this episode as a turning point towards more continuing story arcs on The Next Generation. He commented, "The biggest decision on this show was the ending...where Worf takes it on the chin and decides to accept his dishonor even though he knows its a lie but he does it for the greater glory of the Empire and he walks out the door and it ends with this sense of 'Oh my God. This has changed Worf forever, and what's going to happen to him next?' And what that did to the franchise overall was it suddenly said there's a continuing story here...As soon as Worf walks out the door with his dishonor it demands a follow-up. And that's why we eventually came back to "Reunion" and "Redemption" and on and on and on. All the Worf stories spring from that moment, and also opened up the whole franchise to the idea that maybe we can do continuing stories. It was really a pivotal moment looking back on how we structured Next Generation." (Chronicles from the Final Frontier, TNG Season 4 DVD special features)

Michael Dorn observed, "There was a lot more involved in it than the writers realized. Things that have to do with Klingon loyalty and honor. They didn't give it its due. You look at Worf in a different light, and I've played him in a different light since that episode. This is not something they have come up with. I'm doing this on my own. Hey, it's their fault. They wrote it. So now, I'm going to carry on with it." (Captains' Logs: The Unauthorized Complete Trek Voyages, pp. 193-194)

The episode was one of three selected for inclusion in the Star Trek: The Next Generation - The Next Level sampler disc intended as a preview of the remastering process for The Next Generation. Amongst the adaptations required to bring the episode up to high-definition quality included a restaging of the opening shot as a digital matte painting, and a new image of Qo'noS by Max Gabl (as the original was output directly to videotape using Video Toaster, and did not exist as a film element). [3]

One complication arose with this episode: thirteen seconds of the original film negative - the first part of the scene in Act Four where Crusher and Riker discuss the discovery of the additional survivor, Kahlest - could not be located. As a result, this sequence had to be upgraded from the standard definition master tape. [4] On 11 April 2012 director Robert Meyer Burnett confirmed that the missing thirteen seconds were located and will be included in the TNG Season 3 Blu-ray, [5] and a preview of the fully-restored scene was included in the TNG Season 1 Blu-ray bonus features.